Method and apparatus for burning fuel



Oct. 26, 1937. p 2,096,765

METHOD AND APPARATUS FOR BURNING FUEL Filed June 21, 1933 INVENTOR Aaiio 2 152122 ATTORN EYS Patented Oct. 26 193 7 UNITED STATES PATENT OFFICE Aatto P. Saba, New York, N. Y. Application June 21, 1933, Serial No. 676,780 4 Claims. '(cl. 11o-2a) My present invention is concerned with a method of and apparatus for effecting the combustion of fuels in suspension and it is more particularly concerned with an improved method of 5 burning comminuted fuel, such as pulverized coke,

mote not only substantially complete and perfect combustion but a high intensity of combustion and a high rate of heat transmission by radiation from the flame. In other words with my apparatus and method there is effected an increased release of heat per unit volume of the furnace or combustion chamber and a large portion of the total energy liberated is transmitted by radiation from the flame.

Another object is to provide a method and apparatus of this character which insures rapid ignition and stable combustion. I

Other objects are to provide an apparatus of simple, practical construction, dependable in operation, rugged and durable in use and capable of effecting substantial fuel economy due to efficiency of operation, and to provide an apparatus of this character which is of compact, inexpensive construction.

Broadly considered the method involves the formation of a free vortex of air, moving circumferentially with a tangential velocity component and progressing with both radial and axial velocity components and the delivery of fuel to the core of the vortex the surface of which is the most rapidly rotating part of the vortex, thereby efl'ect- 40 stream, in such a fashion that the solid particles are moved continuously through fresh portions of the air. The result is that substantially complete and perfect combustion maybe efiected in a combustion chamber of relatively small volume,

the burning fuel taking the form of a luminous flame having a comparatively high radiating power.

The method is carried out in a combustion chamber or furnace which may be considered as 5 a passage for air and products of combustion having walls which are surfaces of revolution and containing a continuous body of fluid passing through it in a form of a free vortex. In a free vortex motion, the fluid moves with velocities such 55 that the velocity of whirl or tangential (circumferential) component of absolute velocity varies inversely as the radial distance from the axis. By free vortex is meant any rotating body of fluid in which the tangential velocity varies inversely as the distance from the axis of rotation. Further discussion of vortices, which support this definition, may be found in Hydraulics" by A. H. Gibson, page 103, published by Van Nostrand, 1925, and A. S. M. E. Transactions, 1921, paper 1824: Present Trend of Turbine Development" by L. F. Moody.

If a fluid while moving as a free vortex moves in an axial direction it is a free spiral vortex. By a free spiral vortex is meant that species of a free vortex in which the moving fluid has an axial velocity component. Inasmuch as the absolute velocity of each portion of a free spiral vortex is the same, each concentric portion thereof will pursue a different spiral course. The spiral currents nearer the axis possess a larger tangential velocity component and a smaller axial velocity component, and the spiral air currents near the outside of the vortex possess a smaller tangential velocity component and a larger axial velocity component.

- A core is formed along the axis of the vortex, in which core the fluid is rotating with a constant angular velocity and with substantially no axial velocity. In the core, therefore, the tangential velocity component is directly proportional to the radial distance from the axis.

When the combustion chamber has walls which are surfacesv of revolution, it will be obvious that the air current in the core will be rotating with a tangential velocity which increases as the distance from the axis of the core but without a substantial axial movement through the combustion chamber. This tangential velocity of the core reaches a maximum at its periphery. The inner layer of the free vortex will have the same movement as the outer layer of the core and will in effect he the same. However, each succeeding outer layer of the free vortex will be moving'with a slower tangential velocity component and greater axial velocity component.

The fuel to be burned is delivered preferably into the core of the vortex. The fuel particles will travel radially outward through the core and into and through the air streams of the free spiral vortex. The centrifugal force will act continuously to move the particles into new regions of the spirally progressing air streams of thevortex.

It is evident that with luminous combustion, the speed of combustion is controlled by the rate for accelerating the reaction consists in a violent destruction of the separating layers of products of combustion and the equalization of the oxygen concentration near the particles by most rapid relative motion between the solid particles and Bases.

While the particles rapidly acquire the velocity of any air stream in which they find themselves, they, however may be diverted from the carrying stream by centrifugal force developed when the carrying air is moving in a curved path.

The fuel particles introduced into the core will move outwardly due to the centrifugal force until they reach the outer layer of the core and will then move into the air currents of the free vortex. Inasmuch as these currents have an axial velocity component the particles will begin their travel through the length of the combustion chamber. The centrifugal force acting on the fuel particles will move them outwardly through or combustion chambers for carrying out the method. The preferable form of the combustion chamber is such that the confining walls of the same are surfaces of revolution. But it is understood that a combustion chamber of polygonal cross-section, may be used because the main air stream lines will move in substantially spiral The invention may be more fully understood from the following description in connection with the accompanying drawing whereinz- Fig. l is a fragmentary longitudinal sectional view through a fuel mixing and combustion chamber embodying the invention, the view being somewhat diagrammatic in its showing of the means for forming the vortex in air and means for injecting fuel,

Figs. 2 and 8 are transverse sectional views on the lines 2-! and 3-4 respectively of Fig. 1,

Fig. 4 is a view similar to Fig. l but showing the application of the invention to a boiler,

Fig. 5 is a transverse sectional view on the line 5-5 of Fig. 4, and

0,090,705 I v i for fuel. The fuel is introduced through a volute casing il having a tangential fuel inlet II. The opening ll through which the fuel discharges into the combustion supporting air is formed at the end of a generally frusto-conical upward extension ii of the casing ll.

'I'hevolutecssingilwillimparttofuelparticles entering the inlet II the motion of a free vortex as they exitfroni the opening it.

For the sake of clarity I have omitted any showing of the apparatus for forcing liquid, gaseous or puiverulent fuel through the casing II and um have not shown the usual mechanism for producing a powerful blast of air through the inlet ii of the casing ll.

It will be apparent that as the fuel is introduced it tends to partake of the movement of the air in the core. If fuel is introduced through the casing II and ignited, the combustion proceeds from a the contacting boundary of the core and the annular air stream of the free vortex, and. as

, perature to ignite the same. Stable combustible Fig. 8 is a transverse sectional view on the line M of Fig. 4.

Referring first to the form of invention illustrated in Figs. 1 to 3 of the drawing, I have used the reference numeral II to designate a volute casing having a tangential air inlet ll through which the air is introduced into the casing. 1n-

iloat it into the combustion chamber.

gases make contact with the oxygen of the air and are burned. Due to the rotation of the core, the fuel particles will pass through the contacting boundary of the streams of the core and the free spiral vortex, and into the combustion-supporting air of the free vortex. The thorough combustion of these particles is supported as they progress radially and axially in their course through the free spiral vortex. Combustion is completed within the furnace by the time the particles reach the periphery of the free spiral vortex and the ash remaining is removed with the products of combustion.

Where pulverized coal is used it is introduced I with only a sufficient mount of carrying air to Thus the thermal capacity of the fuel cloud is reduced to a minimum and its ignition is accelerated. Under such conditions the pulverized coal is rapidly ignited as it reaches the burning zone and the burning coal particles move continuously into zones of fresh air as they whirl in a spiral path toward the outside of the vortex and up the fiue. In the firing of bituminous coal powder the combustion process is such that the powder is gasified just before it reaches the combustion zone.

Inthestructureillustrated,inl"igs.4to inclusive, the combustion occurs wholly within thechamberll whichinthisinstanceiss'hown encircled by a jacket 2i containing water to be converted into steam. Here the fuel is intro-' duced through a straight nozzle 22 coaxial with the cylindrical air inlet chamber 2. and projecting axially through this chamber into casing II.

wardlycurvingvanesllinthecasingservetodirect the air toward the center of the casing and to create a free vortex of air which progresses axially through the furnace or fiue It due to the pressure of air entering the inlet ii. The volute casing ll communicates at its top with the fiue II and at its bottom in axial alignment with the-fiue there is provided an inlet ll to forma free vortex withinthe coreof whichthe fuel injector nozzle 12 is disposed.

The air inlet casing in this instance is found with a circular series of spaced tangential vanes .24. A volutecasing ii at the top of the furnace is connected to an exhaust fan (not shown) to induce the entry of air into chamber 20, as well as to increase the absolute velocity of rotation. The vane arrangement causes the induced draft The fuel may be injected through the male '22 by any suitable means. Liquid fuel may be injected by an air atomizer or a mechanical atomizer. Pulverized coal may be carried through in a stream of air. Ignition takes place in the core and the combustion of the particles begins at the contacting boundary of the core and the annular air stream of the free vortex and the fuel particles actuatedLboth by centrifugal force and by the drag of the free vortex move through the combustion-supporting air in radially and axially progressing spirals until they are completely burned.

It will thus be seen that there is herein described apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and is well suited to meet the requirements of practical use.

As many changes could be made in the details of the apparatus, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that the forms shown in the accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

LAn apparatus for burning solid powdered fuel in suspension comprising in combination a combustion chamber having an interior surface of a transverse cross sectional shape to maintain a free spiral vortex therein and having an air inlet at one end thereof, means at said air inlet end of the combustion chamber for introducing air in the form of a free spiral vortex into the combustion chamber, the proportions of the combustion chamber in respect to said means for producing the vortex being such that the air is tion from said chamber.

maintained in a free spiral vortex within the combustion chamber, and a fuel inlet at one end of the combustion chamber for introducing the solid powdered fuel into the core of the vortex.

2. An apparatus for burning solid powdered fuel in suspension comprising in combination a substantially cylindrical combustion chamber having an air inlet at one end thereof, means at the air inlet end of the combustion chamber for introducing air in the form of a free spiral vortex into the combustion chamber, the proportions of the combustion chamber in respect to said means for producing the vortex being such that the air is maintained in a free spiral vortex within the combustion chamber, and a fuel inlet at one end of the combustion chamber for introducing the solid powdered fuel into the core of the vortex.

3. A method of effecting combustion of comminuted fuel in suspension, which includes the steps of creating and maintaining a free spiral vortex of combustion-supporting air, introducing the fuel into the core of the free spiral vortex of air, whereby ignition occurs at the common boundary of the core and the combustion-supporting air and burning continues as the fuel particles move in expanding spirals through the free vortex.

4. The combination with a cylindric combustion chamber having flaring ends, of means at one end of said chamber for admitting air tangentially thereto, means at said end for delivering solid powdered fuel axially into said chamber,

and a volute casing at the opposite end of said chamber for delivering the products of combus- AA'ITO P. SAI-IA. 

